Rotary offset printing press roll support



ROTARY .OFFSET PRINTING PRESS ROLL SUPPORT Filed Nov. 4, 1953 Jan. 22, 1957 STEMPEL 2 Sheets-Sheet 1 INVENI'OR 4175240 M. .s7z-vvxas,

ATTORNEYS Jan. 22, 1957 M. STEMPEL 2,778,303

ROTARY OFFSET PRINTING PRESS ROLL SUPPORT Filed Nov. 4, 1955 2 Sheets-Sheet 2 -57 INVENTOR 572-MPEL,

Mal-M 5 5 ATTORNEYS United States Patent ROTARY OFFSET PRINTING PRESS ROLL SUPPORT Laszlo M. Stempel, Metuchen, N. J., assignor to John Waidron Corporation, New Brunswick, N. 3., a corporation of New Jersey Application November 4, 1953, Serial No. 390,133

11 Claims. (Cl. 101-218) This invention relates to rotary three cylinder printing presses and more particularly to ofisetprinting presses equipped with improved means to eliminate plate damage and printing inequalities resulting from relative cylinder movement on loss of contact or reduction in pressure between one or more pairs of cylinders caused by discontinuities in the printing plate and offset blanket.

It is a general object of the present invention to provide novel and improved apparatus for rotary printing presses so constructed as to prevent printing inequalities even at high speeds.

More particularly it is an object of the invention to provide means for supporting the blanket cylinder wholly independent of the impression cylinder whereby adjustments may be made to accommodate various paper thicknesses without changing the printing quality.

An important object of the invention resides in the means for preventing vibration of the plate, blanket and impression cylinders of a rotary offset printing press including supports for the blanket cylinder wholly independent of the bearings therefor or the contact with the impression cylinder.

A further important object of the present invention resides in the provision of a blanket cylinder having the usual gap in the surface thereof and fitted with bearers of contact diameter for engagement with similar bearers on the plate cylinder, of an impression cylinder for pressing the material to be printed against the blanket cylinder and having necks opposite the blanket cylinder bearers, together with support rings loosely surrounding said necks and urged against the blanket cylinder bearers by means wholly independent of the impression cylinder.

Other and further objects and features of the present invention will be more clearly understood by those skilled in the art upon a consideration of the accompanying drawings and following specification wherein is disclosed a single exemplary embodiment of the invention with the understanding that such changes and modifications may be made therein as fall within the scope of the appended claims without departing from the spirit of the invention.

In said drawings:

Fig. 1 is an end elevation of that portion of a web-fed offset-type printing press pertaining to the present invention, certain parts of the frame being broken away to better illustrate the engagement of the several cylinder bearers; and

Fig. 2 is a fragmentary section, showing one end only of the cylinders, taken on line 2-2 of Fig. 1.

Printing presses of the rotary offset type, and particularly where web fed, have long been restricted to relatively slow operation if high grade impressions are desired. Attempts to speed up these presses have resulted in inequalities in the printing density, referred to by various names in the trade depending upon their general appearance. Said inequalities may comprise sharp extra black impressions, known as friars, occurring in narrow stripes across the width of the web.. Other heavier 2,778,303 Patented Jan. 22, 1957 impressions more extensive in character may be referred to as slurs or blurring of the impression, the latter showing evidences of relative movement between the web and printing surface. Additional forms of printing inequalities may include stripes of lighter than normal impression density. One common cause of all of these is the gaps in the plate and blanket rollers resulting from the necessity for securing a non-tubular plate and blanket to these cylinders, while another is the need for impression cylinder adjustment to accommodate various thicknesses of paper or other web to be printed.

The plate cylinder, usually the top one in a stack of three, has a continuous, highly accurate cylindrical surface except for a narrowlongitudinal gap which receives the inturned ends of theplate and the locking wedge for holding it in position. Some corresponding means is used for attaching the ends of the blanket, which is the resili ent cover for the intermediate cylinder which receives the inked impression from the plate. The plate is inked by some conventional ink depositing mechanism including distributing rolls and the impression transferred by it to the blanket is in turn transferred to the web, which is pressed against the under surface of the blanket cylinder by the impression cylinder, the third and lowermost one in the stack.

The gaps in the plate and blanket cylinders, where the ends of the respective covers are secured thereto, meet each other in all but exceptional cases once per revolution and during the time of impression on the web, since these two cylinders are, in all but rare cases, of the same diameter. The gap in the blanket cylinder passes over the web on the surface of the impression cylinder at a time when no impression is being transferred to the web. Both of the above enumerated meetings result in a relief of the respective pressures ordinarily existing between the contacting cylinders or their coverings.

During operation of the press relatively light pressure must be maintained between the plate and blanket cylinders and considerably heavier pressure between the blanket and impression cylinders. The plate and the blanket run in direct contact and the pressure is controlled by using underlays under one or the other or both. The distance between cylinder centers cannot be adjusted for pressure regulation because of the need for contact between the bearers on these cylinders to be later described. If the plate and blanket were of ideal thickness no underlays would be required.

The web to be printed runs between the blanket and the hard faced impression cylinder. If the press was to be designed for a fixed thickness of web the pressure could be fixed at the desired amount and the proper position of the cylinders relative to each other could be maintained by contacting bearers between the cylinders. However for practical reasons provision must be made for various thickness of web to be printed and the impression cylinder must be adjustable in position to achieve the proper impression pressure.

It is now almost universal practice to provide the plate and blanket cylinders with a bearer at each end to hold the cylinders in the proper positions when the gaps in their cylindrical surfaces meet each other. Such bearers comprise cylindrical discs of hard metal coaxial with the cylinders and having a diameter such that the bearers may be said to engage each other at the contact diameter of the engaging cylinders. Thus on the blanket cylinder the bearers will be of larger diameter than the metal cylinder to compensate for the thickness of the blanket. All three press cylinders are geared together to have a common peripheral speed irrespective of their diameters, and the same must be true of the surfaces of the bearers if no slippage is to result. These bearers are held together at suitable pressure by the cylinder bearings and because of their continuous surfaces tend to prevent the shock of gap meeting. However, no bearers rigidly fixed to the impression cylinder can be used for reasons pointed out above, so that when the gap in the cylindrical surface of the blanket faces the impression cylinder the blanket cylinder tends to jump toward the impression cylinder since the high nip pressure normally existing between the cylinders is abruptly reduced to zero while the plate cylinder-blanket cylinder nip pressure is not reduced. This unloads the blanket cylinder bearings and aided by gravity the cylinder moves downwardly closer to the impression cylinder. This momentary jump disturbs the pressure between the plate and blanket cylinders and interferes with the proper transfer of ink from the plate to the blanket. The result of this shows up as a reduced density band across the printed web. Then when the pressure is suddenly built up again a hammering action results which ultimately causes the plate to crack across its width where this action occurs. It may also produce a slur or friar by the increase in blanket-plate pressure momentarily.

In accordance with the present invention the above difficulties are eliminated by providing supporting discs or rings for the blanket cylinder which are entirely free of any connection or contact with the impression cylinder and which are resiliently urgedinto tight engagement with the bearers on the blanket cylinder.

The invention will be more fully understood by reference to the drawings, which illustrate only so much of the printing apparatus as is essential to an understanding of the novel features. Referring now to these drawings, it will be seen that the upper frame constructions on each side of the press are adapted to be supported from base frames 11, to provide bearings for the several cylinders about to be described. These frames are of appropriate rigid construction and thickness and provided, as seen in Fig. 2, with circular apertures 12, 13, and 14 for the reception of bearing members 15, 16, and 17 adjustably rotatable therein and appropriately bushed as shown to provide bearings for the journals 18, 19, and 20 of the impression cylinder 22, the blanket cylinder 23 and the plate cylinder 24, respectively. At least two of the bearings have the bushings eccentric therein. As seen in Fig. 2, only one end of the apparatus is illustrated, but it will be appreciated that it is duplicated at the other end in so far as the bearings and like parts are concerned and the cylinder journal extensions may also be provided with meshing drive gears or the like which form no part of the invention.

The eccentric bearing elements and 16 are individually adjustable to adjust the contact pressures between the respective cylinders for the reasons pointed out above, and may be simultaneously adjustable through a wider range to remove the press from impression when it is desired, as will be appreciated by those conversant with this type of apparatus.

The uppermost cylinder 24 of the stack is adapted to have wrapped about its cylindrical surface a suitable plate of thin metal or plastic material on which the relief or lithograph printing surface are provided by engraving, etching, photo-lithography or the like. The impression areas, not shown, are inked by conventional inking mechanism for transfer to the blanket on the cylindrical surface of cylinder 23. This has not been illustrated but comprises a relatively heavy layer of resilient material of rubber-like consistency on which the impression is taken from the inked plate.

The plate being made in the plane form must be bent about the cylinder 24 and its ends turned down and received in the narrow slot or gap 26 therein, which is subsequently filled with a wedge of some character to hold the plate tightly stretched about the cylinder. Naturally the outer surface of this wedge cannot be entirely co-extens ive with the surface of the plate and is one of the sources of vibration or jump.

The rubber-like blanket being made in continuous linear form must be wrapped about the blanket cylinder and the ends secured beneath its surface in some recognized manner, which results in a gap such as shown at 27 in the cylinder 23.

The impression cylinder 22 is merely a hard faced steel cylinder of smooth continuous exterior configuration.

At the ends of the major diameter portion of each of the cylinders 23 and 24 there are reduced diameter necks, such as at 30 on cylinder 24, on which is rotatably mounted a collar including an eccentric rim 31 for forcing and holding the plate wedge in position. A similar collar 32 appears on the neck 33 of blanket cylinder 23. Outwardly beyond these each of the plate and blanket cylinders is fitted or has formed integral therewith a bearer 35, 36, preferably of hardened metal with a true exterior cylindrical surface, each of contact diameter of its cylinder whereby both the cylinder covered surfaces and the bearers run together without slippage.

These bearer discs are tightly compressed against each other by the initial adjustment of the eccentric bearings for the respective cylinders and serve to a large degree to limit vibrations when the gaps come together. To prevent jump when the blanket gap faces the impression cylinder and to stabilize the load on the bearings of the blanket cylinder, a supporting ring 38 loosely surrounds the neck 39 at each end of the impression cylinder 22. These rings are in all recognized respects similar to the bearers on the other cylinders except that they are wholly independent of cylinder 22 and merely surround the necks loosely, as clearly seen, for convenience in location. They are tightly pressed against bearers 36 each by the action of two, small diameter, spaced rollers 40, identical in character and of the same length as that of the ring 38. The rollers 40 are mounted on journal pins 41 extending through a pair of metal plates 42 spaced apart a distance slightly greater than the length of the rollers and together comprising a yoke. The upper intermediate portion of the yoke straddles the lower portion of its supporting ring 38, as clearly seen in both figures, and holds it against any substantial longitudinal movement. The center of the yoke is rockably attached to the flattened upper end 44 of a tubular slide element 45 by the transverse pin 46 passing through and secured to the yoke plates by screws asshown in Fig. 2. The tubular plunger 45 is slidable in bore 47 of sleeve 48 mounted by means of the thickened portion 49 against the inner face of base frame 11 and positioned thereon by studs 50 received in threaded openings. The extended axis of sliding of the plunger 45 passes through the axes of cylinders 22 and 23.

The enlarged lower end 51 of sleeve 48 receives a lower cover plate 52 held thereon by studs 53 which is centrally bored and threaded to position adjusting screw 54 fitted with lock nut 55. This screw thrusts against a spring base 56 fitted within and below the helical spring 57 mounted with the hollow plunger 45 and bearing against the top of the bore therein. This spring when compressed provides for the resilient thrusting of the rollers against the ring 38 to urge it against the bearer disc 36 on the blanket cylinder for the purpose defined above.

The combination of resilient support of the blanket cylinder through the action of its support rings and the yoke parts and the spring biasing of the yokes acting together with the bearers on the plate and blanket cylinders assures of smooth operation of the press under all circumstances and at all speeds. The separation of all parts of the impression roll from metal to metal contact with any parts of the blanket roll achieves a smoothness of operation and freedom from irregularities in printing such as have not heretofore been known.

I claim:

1. In a rotary type printing press having a plate cylinder for mounting a circumferentially discontinuous printing plate thereon, a blanket cylinder for mounting a printing blanket thereon, and an impression cylinder having a continuous cylindrical surface, means providing bearings positioning the first and second cylinders to con tact plate and blanket and the second and third cylinders to contact blanket and surface, the combination of cylindrical bearers fixed rigidly on the ends of the first and second cylinders of contact diameters and held in engagement with each other by said bearings, means to adjust the bearings of the impression cylinder to change its contact pressure with the blanket, free running support rings one loosely surrounding but wholly dependent of and radially spaced from a reduced neck on each end of the third cylinder and means independent of said necks supporting and urging said rings against the bearers on the blanket cylinder at a pressure independent of the adjusted pressure between blanket and impression cylinders.

2. The combination recited in claim 1 wherein the support means each comprise a pair of rollers, a mounting yoke for and pivoting the rollers and means holding the rollers against the ring in a direction toward the axis of the blanket cylinder.

3. The combination recited in claim 2 in which the yoke is engaged by resilient means adjustable to hold the rings against said blanket cylinder bearers with a predetermined load.

4. The combination recited in claim 2 in which resilient means urge the yokes toward the rings.

5. The combination with a rotary type printing press having substantially peripherally contacting plate, blanket and impression cylinders of conventional offset printing character, each of said plate and blanket cylinders having end bearer discs of contact diameter held in engagement by cylinder bearings; of necks on the ends of the impression cylinder between the effective portion thereof and the bearing journals, a ring surrounding each neck and free of engagement therewith, and means engaging the peripheries of and supporting said rings in rolling engagement with the bearers on said blanket cylinder, whereby the rings need not be of contact diameter.

.6. The combination recited in claim 5 wherein each said ring is rotatably positioned by a pair of rollers spaced on opposite sides of a plane through the axes of the blanket and impression rollers.

7. The combination recited in claim 6 wherein said rollers are spring pressed against said rings in the direction of said plane.

8. The combination recited in claim '7 in which adjustable resilient means resist the movement of the rings in a direction opposite to that of the spring urge.

9. The combination as recited in claim 6 wherein the rollers of said pair of rollers for each ring are mounted at the ends of yoke and compression spring means urging the center of said yoke toward and along a plane passing through the axes of the blanket and impression cylinders.

10. The combination as recited in claim 9 in which means carried by each said yoke provides side guides for the rings supported by the yoke mounted rollers.

11. The combination with a rotary type printing press having successively substantially contacting plate, blanket and impression cylinders of conventional oifset printing character, bearings mounted said cylinders in normally fixed relation, a disc-like bearer of contact diameter on each end of the plate and blanket cylinders and running References Cited in the file of this patent UNITED STATES PATENTS 2,362,069 Huck Nov. 7, 1944 2,581,593 Luttenauer Jan. 8, 1952 2,598,726 Stempel June 3, 1952 FOREIGN PATENTS 3,076 Great Britain June 24, 1914 63,143 Switzerland Feb. 8, 1913 350,655 Great Britain June 18, 1931 

